A. Field of the Invention
The field of the present invention relates generally to methods and systems for cleaning large elongated structures such as heat exchanger tube bundles, fin-fans, cooling towers and the like. In particular, the present invention relates to such methods and systems that are configured to be portable so they may be moved to the location of the structure and used on-site. Even more particularly, the present invention relates to such methods and systems that are able to utilize site-produced cleaning fluids, reprocess waste fluids on-site and contain all exhaust gases so as to clean such structures in an economically and environmentally-friendly manner.
B. Background
Many types of facilities utilize heat exchanger systems having heat exchanger tube bundles, fin-fan cooling apparatuses, cooling towers and the like. One industry in particular that utilizes many such heat exchanger systems is the petroleum refining industry. The efficiency of the heat exchanger affects the rate of producing product and the cost of the final product As well known by those skilled in the art, heat exchangers are prone to fouling, with the frequency and extent of the fouling generally dependent on the type of fluids that flow within the heat exchanger. A fouled heat exchanger will adversely affect the production rate and increase the cost of producing the product, primarily as a result of the fact that the temperature of the heating fluid must rise if heat is to be transferred by the tube bundles or other components to the fluid flowing within the tubes or other apparatuses. As such, it is common to monitor the heat exchange efficiency of the heat exchanger and to periodically, or even routinely, clean the fouled components thereof so as to maintain as close to an optimum operating criteria as possible for the heat exchanger.
Cleaning heat exchanger components generally requires the heat exchanger, and therefore usually the associated production line, be taken off-line. One common method of cleaning heat exchanger components, such as heat exchanger tube bundles, is to remove the tube bundles from the heat exchanger and then direct a very high-pressure spray of fluid, typically water, against the outer surface of the tube bundles. Unfortunately, blasting water at high pressure against the outer surface of the tube bundles can damage components thereof and push the debris more to the center of the tube bundle where the debris can interfere with the flow of air or other fluids through the tube bundle. In addition, the high pressure spray results in significant waste fluid in the cleaning area and can cause fumes to be released to the atmosphere. An alternative method of cleaning tube bundles and other heat exchanger components is with the use of chemicals, typically mildly acidic compounds, that are directed generally over the components or in which the components soak. To be effective, the chemical compounds must be strong enough to remove the material which is fouling the heat exchanger components and be able to remove the material from the center of the tube bundle or other component. Use of such chemicals require transport of the chemicals to the site where the cleaning is to be performed, transfer of the components to the cleaning site (if not done on-site) and disposal of the liquid and solid waste. Use of chemicals can also result in the release of toxic vapors to the atmosphere. Another alternative cleaning method involves the use of foam or foam-like products that interact with the debris build-up on the tube bundles or other components to dissolve the debris and clean the component. As with the chemical treatment procedures, however, use of foam results in waste products that must be disposed of and can emit toxic vapors to the atmosphere.
As stated above, the primary prior art methods of cleaning fouled tube bundles and other heat exchanger components result in waste liquids that are contaminated with the compounds used in the processing facility and with any compounds that are used to clean the components and results in the release of toxic vapors to the atmosphere. The handling of the often toxic waste liquids and the release of toxic vapors to the atmosphere are increasingly subject to various governmental laws and regulations that are intended to ensure the liquids are properly handled and disposed of and to limit the amount and/or toxicity of the vapors released to the atmosphere. With regard to some types of contaminated liquids and toxic vapors, the laws and regulations can substantially prohibit the release of the liquids or vapors. In general, these laws and regulations are likely only to become more restrictive over time and result in higher costs to clean tube bundles and other heat exchanger components.
To address concerns with regard to prior art methods and systems of cleaning tube bundles and other heat exchanger components, various mechanical systems, including a number of patented devices, systems and methods, have been developed to mechanically clean tube bundles and like structures. One such example is found in U.S. Pat. No. 3,052,245 to Nagle, which describes an apparatus for cleaning heat exchanger tube bundles that comprises a carriage that rotatably supports a tube bundle on one end with a pair of driven rollers and at the opposite end on a pair of idler rollers. High velocity, high pressure jets of hot water are discharged onto the rotating bundle through nozzles carried by a pair of headers supported by a wheeled carriage assembly that moves each header in opposite directions longitudinally along the rotating bundle. Another example of an apparatus for cleaning tube bundles is found in U.S. Pat. No. 3,060,064 to Zingg, which describes a cleaning apparatus that rotatably supports a tube bundle at each end thereof while three nozzles direct a spray toward the tube bundle as the nozzles move longitudinally along the tube bundle while the bundle rotates. One nozzle directs a spray of gas flame, another nozzle directs a spray of steam and the third nozzle directs a jet water or other liquid towards the tube bundle. Water or other coolant fluid is pumped through the tubes from an open reservoir, which may comprise a heater unit to pre-heat the coolant fluid before it is pumped through the tube bundle. U.S. Pat. No. 4,509,544 to Mains, Jr. describes a tube bundle cleaning apparatus having a plurality of high pressure water jets spraying on the tube bundle as it is rotatably supported by a set of power rollers. Jet nozzles are supported by a non-rotatable cleaning head and a rotatable cleaning head that are mounted on a pair of carriages that move along the length of opposite sides of the tube bundle while the water is sprayed thereon. The carriages move back and forth in repeated cycles as the tube bundle is rotated to different angular positions by the power rollers. U.S. Pat. No. 5,018,544 to Boisture describes an apparatus for cleaning tube bundles comprising a truck mounted fluid and hydraulic source, a trailer mounted system for rotatably supporting a tube bundle and a remote control pedestal from which an operator may control the cleaning operations. The trailer mounted system also has an articulatable mobile crane for raising and lowering the tube bundle and a set of outriggers for stabilizing the trailer during cleaning operations.
To address concerns with regard to the discharge of waste liquids and toxic vapors from the tube bundle cleaning operations; several modern systems include mobile units that are configured to be generally self-contained and more environmentally-friendly. For instance, U.S. Pat. No. 5,437,296 to Citino describes a tube bundle cleaning device having a mobile base defining a main reservoir with an interconnected bottom structure that defines a cleaning fluid reservoir. The tube bundle is rotatably supported on roller assemblies inside the main reservoir, above the cleaning fluid reservoir, and a pair of doors enclose the tube bundle therein. Cleaning fluid is placed within the cleaning fluid reservoir and heated to the desired temperature by heating elements inside the cleaning fluid reservoir. The cleaning fluid is pumped from the cleaning fluid reservoir to a separate sump where a main pump assembly pressurizes the cleaning fluid and directs it so a spray nozzle assembly that sprays the cleaning fluid on the tube bundle rotating inside the main reservoir. The sump is in fluid communication with the main reservoir such that filling the sump partially fills the main reservoir and used cleaning fluid from the main reservoir is re-circulated through the sump, filtered and then re-used. The cleaning fluid solution is drained back into the cleaning fluid reservoir and stored for future use or later disposal or reprocessing. U.S. Pat. No. 7,575,641 to Joseph describes a tube bundle cleaning method and system which comprises a similarly configured tube bundle cleaning device except it has a single door that is configured to sealably enclose the tube bundle inside the main reservoir, a vapor lock seal positioned around the top of the reservoir enclosure and a purge system to capture fumes from within enclosed areas of the device and filter the fumes to prevent venting of the fumes to the atmosphere. In use, the cleaning fluid reservoir is filled at the cleaning site with cleaning fluid and emptied after cleaning is complete.
Despite the foregoing, what is needed is an improved cleaning system for cleaning heat exchanger tube bundles, fin-fans, towers and similar elongated structures. The improved cleaning system should more effectively and efficiently clean tube bundles and other such structures. The improved cleaning system should be portable and utilize site available cleaning fluids so the cleaning operations may take place on-site, thereby avoiding the need to transport the structures and/or cleaning fluids. The improved cleaning system may be configured so as to be an entirely self-contained unit and allow the operator to safely and effectively clean tube bundles and like structures without discharging any contaminated fluid or toxic vapors to the environment.